1. Field of the Invention
The present invention relates generally to a nanostructure array substrate, a method for fabricating the same, and an application of the same. More particularly, the present invention relates to a metal oxide nanostructure array substrate, a method for fabricating the same, and a dye-sensitized solar cell using the same.
2. Description of the Related Art
The one-dimensional structures having a nano-scale, such as nanorods or nanowires, have inherent optical and electric characteristics, so the one-dimensional structures have been used for various electronic devices and optical devices.
Korean Unexamined Patent Publication No. 2010-00869592, which has been filed by some of inventers of the present invention, discloses ZnO rods vertically aligned on a substrate while being separated from each other and a method for fabricating the same. A well-aligned nanostructure array having the vertical alignment on the substrate can be formed by using the ZnO rods.
Recently, as the environmental pollution and high-price oil have been issued, development of clean alternative energy has been interested, so various studies and research have been pursued to develop solar cells. Among the solar cells, a dye-sensitized solar cell generally consists of a photo electrode including photosensitive dyes adsorbed in a transparent substrate and a porous oxide nano-particle, an iodine-based electrolyte prepared by dissolving iodine ions undergoing oxidation/reduction reaction in an organic solvent, and a Pt counter electrode. The dye-sensitized solar cell is inexpensive and can be fabricated through a simple process as compared with a conventional silicon solar cell. However, the photoelectric conversion efficiency of the dye-sensitized solar cell is very low, so there are limitations to use the dye-sensitized solar cell in practice.
In order to improve the photoelectric conversion efficiency of the dye-sensitized solar cell, various studies and research have been performed. For instance, there have been suggested methods for increasing adsorption of solar light, increasing generation of electrons by increasing adsorption of dyes, preventing extinction of excited electrons caused by recombination of electrons and holes, and improving mobility of electrons.
Among them, Korean Unexamined Patent Publication No. 2010-0137032 discloses a method for improving a dye adsorption area and mobility of electrons by preparing titanium oxide used in a photo electrode of a dye-sensitized solar cell as a nano-branch, other than porous nano-particles. However, according to the above method, the nano-branch is not vertically aligned on a substrate, but laterally aligned on the substrate and thickness of the electrode is increased at a dye adsorption surface, so the transparency of the substrate may be degraded.
In addition, Korean Unexamined Patent Publication No. 2010-0075032 discloses a method for fabricating a self-aligned titanium nanotube, and Korean Unexamined Patent Publication Nos. 2010-0121116, 2009-0022956 and 2009-0035343 disclose a titanium nanotube and a dye-sensitized solar cell using the same. However, the titanium nanotubes disclosed in the above publications are fabricated through an etching process using the anodizing. The titanium structure referred to as the nanotube may have the porous shape, in which a plurality of holes having a cylinder shape are formed in a titanium substrate. That is, the nanotubes disclosed in the above publications may not be separated from each other, but laterally connected with each other. In this case, the surface area of the titanium oxide to which the dyes are adsorbed may not be greatly increased. In addition, if the titanium nanotubes fabricated through the above methods are applied to a photo electrode of a dye-sensitized solar cell, the transparency of the photo electrode may be degraded, and the light adsorption may be reduced.
That is, there are limitations to improve the photoelectric conversion efficiency of the solar cell by using the conventional technologies, so a new technology is necessary to improve the photoelectric conversion efficiency of the solar cell.
References:
1) KR 2010-0086592 A
2) KR 2010-0137032 A
3) KR 2010-0075032 A
4) KR 2010-0121116 A
5) KR 2009-0022956 A
6) KR 2009-0035343 A